Remove --disk_spill_integrity; merge into --disk_spill_encryption

There appears to be little reason to separate disk spill integrity and
encrytion into two different flags, so this submittal removes the
integrity check flag and makes that functionality available when disk
spill encryption is turned on.

Change-Id: I046966c33422736cb7315f7f378af06b9808a83f
Reviewed-on: http://gerrit.sjc.cloudera.com:8080/4547
Reviewed-by: Alex Behm <alex.behm@cloudera.com>
Tested-by: jenkins